The invention relates generally to hybrid cycle power generation and, more particularly, to a hybrid fuel cell/pulse detonation engine power system.
Fuel cells, for example solid oxide fuel cells (SOFCs), are energy conversion devices that produce electricity by electrochemically combining a fuel and an oxidant across an ion conducting layer. For power generation applications, large numbers of fuel cells arranged in stacks are used to generate electric power.
One challenge facing fuel cell power generation is the long time scale to get to full load. Although the time constants vary by fuel cell type, they typically range from a few hours to days for powers of about a megawatt or more. In contrast, conventional one-hundred watt (100 MW) gas turbines go from cold start to full load in less than about five (5) minutes. Accordingly, it would be desirable to have a rapid start option for power systems that incorporate fuel cells.
Another challenge facing fuel cell power generation is building fuel cells that are large enough to utilize a substantial fraction of the fuel supplied to the fuel cell unit, so that competitive fuel efficiencies can be achieved. Large fuel cells can be expensive and difficult to fabricate. Accordingly, it would be desirable to achieve competitive fuel efficiencies while using smaller, less expensive fuel cells.
Another objective in power system design is increased efficiency, for both simple cycle and combined cycle systems. However, to achieve high cycle efficiencies, both the pressure ratio and the working temperature must be as high as materials and cooling technology permit. Presently, high-pressure ratios are achieved using complex high-pressure compressors and turbines, which help to compensate for the four to seven percent (4–7%) pressure loss results from conventional combustion processes. However, these systems involve numerous pieces of complex rotating machinery.
Recently, efforts have begun to explore the use of pulse detonation engines in aircraft engines. Beneficially, pulse detonation engines produce a pressure rise from a series of repeating detonations or supersonic combustion events. Accordingly, it would be desirable to develop a power system that uses pulse detonations to enhance cycle efficiency. It would also be desirable for the power system to have rapid start capability. In addition, it would be desirable for the power system to achieve competitive fuel efficiencies, while using smaller fuel cells.